This invention relates, in general, to manufacturing semiconductor products, and more particularly, to die bonding a semiconductor die to a flag portion of a semiconductor lead frame.
Bonding of the semiconductor die to the flag portion of the lead frame has been done for a long time. Until recently, the thickness of the die bond material between a semiconductor die and the flag portion of the lead frame has not been an important parameter. However, as the semiconductor die size increases and the semiconductor die thickness decreases, problems occur with the semiconductor die's cracking or breaking because of stress caused by the die bond material. These problems, therefore, have caused a need to measure and to control the thickness of the die bond material between the semiconductor die and the flag portion of the lead frame.
Currently, measurement of the thickness of the die bond material is achieved by an infrequent and a destructive method of cross-sectioning the semiconductor die and the lead frame and measuring the thickness of the die bond material by a scanning electron microscope. This method, while accurately measuring the thickness of the die bond material, destroys the semiconductor die that is being manufactured for sale. Since conventional measurement is destructive and infrequent, process variation and process control can only be measured crudely or approximated.
Additionally, as a larger variety of semiconductor die sizes becomes available, greater flexibility of die bond equipment will be necessary. Current die bond equipment cannot change die size, while keeping die bond material at a constant thickness. This deficiency of current equipment limits the die bond equipment's flexibility with respect to die size.
Therefore, a method and apparatus for accurately measuring the thickness of a die bond that is ongoing and nondestructive would be highly desirable. Additionally, providing both a method and an apparatus which increase flexibility and with improved process control is also desirable.